Big-city police departments in New York and beyond boosted uniformed patrols of transportation hubs Monday after a bombing near Times Square but said the attack appeared to be isolated with no immediate threat to other places.

New York Mayor Bill de Blasio said "you'll see additional officers out in force" as police secure all transit hubs and major sites in the city.

“When we hear about an attack on the subway, it’s incredibly unsettling," de Blasio told a news conference.

The NYPD will secure all transit hubs and major sites in this city. You'll see additional officers out in force. When you see something, say something. Speak up because you could be saving lives.

Airports, train and bus stations, bridges and tunnels were also given more security officials, Gov. Andrew Cuomo said. The patrols will step on and off trains and will provide more bag inspections and surveillance, and state police and the National Guard will double their staffing in the city.

Police canine teams and units with heavy weapons as well as plainclothes officers will provide extra protection around Penn Station and Grand Central Terminal. The Metropolitan Transportation Authority, which includes the Long Island Rail Road and Metro North, will also see more patrols.

"Out of an abundance of caution, we are stepping up security measures at high-profile locations and transportation hubs while the investigation progresses," Cuomo said. "We will remain vigilant."

But Cuomo encouraged everyone "to go about their business and live their lives without fear."

The New York Police Department said there will be a greater presence of officers across the city despite the lack of "other specific and credible threats against NYC at this time."

You will see a greater presence of police personnel throughout the city. There are no other specific and credible threats against NYC at this time. #NYPDprotecting

Kirstjen Nielsen, the secretary of Homeland Security, spoke Monday with de Blasio and Police Commissioner James O’Neill and said federal authorities would assist New York in the investigation.

“The enemy we face is persistent and adaptive,” Nielsen said. “But they should know this: Americans will not be coerced by terrorism, and we will not allow it to become the new normal. We will fight back aggressively and bring terrorists to justice.”

A 27-year-old man, Akayed Ullah, was arrested after a pipe bomb detonated about 7:20 a.m. on a subway platform beneath Times Square. Three people suffered minor injuries, and Ullah was injured.

O’Neill said the attack was a terror-related incident inspired by the Islamic State. But law enforcement officials said Ullah apparently didn’t have direct contact with the terror group.

Eight subway lines that run through Times Square bypassed the station temporarily while police investigated but resumed by 11 a.m. The Port Authority Bus Terminal, the country’s largest bus hub, was also evacuated before reopening.

The #Boston PD is monitoring the current incident in #NewYorkCity & continues contact w/ #NYPD. Although there does not appear to be a specific threat to the Boston area at this time, the #BPD has stepped up patrol near major @MBTA stations & reminds officers to remain vigilant. https://t.co/juNk19c0bP

The House Homeland Security Committee warned in a report this month that as the Islamic State lost militarily in Syria and Iraq, the group was shifting to terror attacks in the U.S. and Europe. Other attacks have included vehicles ramming pedestrians, such as along a bike path in New York on Oct. 31 and a truck attack at a Berlin Christmas market a year ago.

“We must remain vigilant and strengthen our security to prevent more people from being radicalized and do all we can to thwart potential attacks,” Chairman Michael McCaul, R-Texas, said of the report.

Pedestrians jam the back of the Port Authority Bus Terminal following an explosion inside an underground tunnel in the building in New York City on Dec. 11, 2017.(Photo: JASON SZENES, EPA-EFE)